The present invention relates to computer networks, and more particularly to a method and system in an Internet Protocol (IP) network for automatically and optimally selecting a Telecommunications Network (xe2x80x9cTelnetxe2x80x9d) 3270 Server according to response time and availability criteria.
SNA and IP Environment
Every day, for all sorts of reasons, more and more companies are focusing on the consolidation of the multiple specialized networks they directly operate or lease from service providers onto a single protocol network. These multiple specialized networks are based on diverse networking technologies such as Systems Network Architecture (SNA), Internet Protocol (IP) or Internetwork Packet Exchange (IPX).
These companies are making this consolidation one of their top priorities. Companies are almost exclusively selecting the Internet Protocol (IP) as their protocol of choice. However, for the overwhelming majority of these companies using SNA protocols and applications, there still is and will be for the many years to come, a major requirement in this changing environment. The requirement is for the employees of these companies to keep the capability they always had to access the huge amount of existing corporate data residing in traditional mainframes and accessible through SNA applications.
TCP/IP
The Internet is a global network of computers and computers networks. The Internet connects computers that use a variety of different operating systems and languages, including UNIX, DOS, Windows, Macintosh, and others. To permit communication among these various systems and languages, the Internet uses a standard language referred to as TCP/IP (xe2x80x9cTransmission Control Protocol/Internet Protocolxe2x80x9d). The TCP/IP protocol supports three basic applications on the Internet: transmitting and receiving electronic mail, logging into remote computers (xe2x80x9cTelecommunications Networkxe2x80x9d or xe2x80x9cTelnetxe2x80x9d), and transferring files and programs from one computer to another (xe2x80x9cFTPxe2x80x9d or xe2x80x9cFile Transfer Protocolxe2x80x9d).
World Wide Web
With the increasing size and complexity of the Internet, tools, often called navigators or navigation systems, have been developed to help find information on the network. Navigation systems that have been developed include programs such as Archie, Gopher and WAIS. The World Wide Web (xe2x80x9cWWWxe2x80x9d or xe2x80x9cthe Webxe2x80x9d) is a recent superior navigation system. The Web is:
an Internet-based navigation system,
an information distribution and management system, and
a dynamic format for communication.
The Web seamlessly integrates several forms of information, including still images, text, audio and video. A user on the Web using a Graphical User Interface (xe2x80x9cGUIxe2x80x9d, pronounced xe2x80x9cgooeyxe2x80x9d) may transparently communicate with different host computers on the Internet different system applications (including FTP and Telnet), and different information formats for files and documents including, for example, text, sound and graphics.
Hypermedia
The Web uses hypertext and hypermedia. Hypertext is a subset of hypermedia and refers to computer-based xe2x80x9clinksxe2x80x9d through which uses move from one place to another in a document, or to another document, in a non-linear manner. To accomplish this feature, the Web uses a client-server architecture. The user""s computer is said to be a client computer to the Web server computer. Web servers enable a user to access hypertext and hypermedia. The clients send requests to the Web servers, which in turn react, search and respond. The Web allows client-based application softwares to request and receive hypermedia documents (including formatted text, audio, video and graphics) from a Web file server with hypertext link capabilities to other hypermedia documents.
The Web, then, can be viewed as a collection of document files residing on Web host computers that are interconnected by hyperlinks using networking protocols, forming a virtual xe2x80x9cwebxe2x80x9d that spans the Internet.
Uniform Resource Locators
A resource on the Internet may be unambiguously identified by a Uniform Resource Locator (URL), which is a pointer to a particular resource at a particular location. A URL specifies the protocol used to access a server (e.g. http://, ftp://, etc.), the name of the server (e.g. www.ibm.com, and the location of a file on that server (e.g. /products/catalog.html).
HyperText Transfer Protocol (HTTP)
Each Web page may appear as a complex document that integrates many media, for example, text, images, sounds and animation. Each such page may also contain hyperlinks to other Web documents, so that a user at a client computer may click on icons using a mouse and may activate hyperlink jumps to a new page (which is a graphical representation of another document file) on the same or a different Web server.
A Web Server is a software program run on a Web host computer that responds to requests from Web Clients, typically over the Internet. All Web servers use a language or protocol to communicate with Web Clients which is called HyperText Transfer Protocol (xe2x80x9cHTTPxe2x80x9d) graphics, sound and video. All types of data, including HyperText Markup Language (xe2x80x9cHTMLxe2x80x9d), can be exchanged among Web servers and clients using this protocol. HTML describes the layout, contents and hyperlinks of the documents and pages to be displayed to the user. When browsing, Web Clients convert user-specified commands into HTTP GET requests, connect to the appropriate Web Server to obtain the information, and await a response. The response from the server may be the requested document or an error message. After a document or an error message is returned, the connection between the Web client and the Web server is closed.
The first version of HTTP is a stateless protocol. That is to say, with HTTP version 1.0, there are no continuous connections between clients and servers. A Web client using HTTP receives a response as HTML data or other data. Newer versions of HTTP break this barrier of a stateless protocol by keeping the connection between the server and client alive under certain conditions.
Browser
After receipt, the Web Client formats and presents the data or activates an ancillary application, such as a sound player, to present the data. To do this, the server or the client first determines the type of data to be received. The Web Client is also referred to as the xe2x80x9cWeb Browser,xe2x80x9d since it in fact browses documents retrieved from the Web Servers.
Telnet 3270
A widely used technique for the transport of SNA information across an IP network is the use of Telnet technologies, specifically the Telnet 3270 (xe2x80x9cTN3270xe2x80x9d) emulation. This technique for SNA xe2x80x9cgreen screenxe2x80x9d workstation users utilizes a Client/Server approach. xe2x80x9cHost-On Demandxe2x80x9d from IBM or xe2x80x9cWebClientxe2x80x9d from CISCO are examples of Client software implementations. Network Utility from IBM or CISCO router""s offerings are typical server implementations (hardware and software). The xe2x80x9cTN3270 Clientxe2x80x9d software usually runs within the customer""s workstation while the xe2x80x9cTN3270 Serverxe2x80x9d software is usually placed in front of the customer""s data center mainframes (or sometimes directly within the mainframe itself) or within the customer""s branch offices.
As illustrated in FIG. 1, IP protocols are used between the TN3270 Server 102 and the TN3270 Clients 101, while traditional SNA protocols are used between the TN3270 Server 102 and the target SNA applications 103. More information concerning Telnet, TN3270 and Network Utility can be found in the following publications, incorporated herewith by reference:
xe2x80x9cTCP/IP Tutorial and Technical Overview,xe2x80x9d Martin W. Murhammer, Orcun Atakan, Stefan Bretz, Larry R. Pugh, Kazunari Suzuki, David H. Wood, IBM International Technical Support Organization, October 1998, GG24-3376-05.
xe2x80x9cIBM 2216/Network Utility Host Channel Connection,xe2x80x9d Erol Lengerli, Jacinta Carbonell, Thomas Grueter; IBM International Technical Support Organization, January 1999, SG24-5303-00.
xe2x80x9cIBM Network Utility Description and Configuration Scenarios,xe2x80x9d Tim Kearby, Peter Gayek, Gallus Schlegel, Imre Szabo, Zhi-Yong Zhang; IBM International Technical Support Organization, January 1999, SG24-5289-00.
xe2x80x9cInternetworking with TCP/IPxe2x80x94Volume Ixe2x80x94Principles, Protocols, and Architecture,xe2x80x9d Douglas E. Comer, Second Edition, Prentice Hall 1991.
Requests For Comments (RFCs) from the Internet Engineering Task Force (IETF):
RFC 1576: TN3270 Current Practices,
RFC 1646: TN3270 Extensions for LU name and Printer Selection,
RFC 1647: TN3270 Enhancements, and
RFC 2355: TN3270 Enhancements.
Accessing SNA Application via Traditional SNA End-to-End
In the traditional SNA world, user workstations traditionally obtain access to SNA applications by connecting first to an intermediate application. This intermediate application provides for access to the real target application. This intermediate application, also referred to as an Intermediate Selection Application, usually displays to the user a selection screen which lists the SNA applications that may be accessed. The user selects from that menu the target SNA application he wants to access and is then connected to that target SNA application, which usually presents to the user an application welcome screen (for instance displaying the SNA application name and asking for a user logon and password). FIG. 2 describes a traditional SNA access to an Intermediate Selection Application in an SNA environment.
First step 201: The user is presented a Selection Screen of a plurality of possible applications by the Intermediate Selection Application (three possible applications A, B and C). Usually, the workstation automatically sets up a direct connection to the Intermediate Selection Application, as soon as the workstation""s SNA protocol stack is started (or, in case of a xe2x80x9cdumbxe2x80x9d terminal, when the terminal is powered on). Second step 202: Provided that at this time the Intermediate Selection Application is up and running, the connected user selects an application (application A) by typing an application name on the selection screen. Third step 203: Finally, the user is connected to the desired application (application A), which usually presents to the user an application welcome screen.
Accessing SNA Application from TN3270 Client with Manual Configuration
TN3270 Clients can be manually configured with the IP address or name of the TN3270 Server which needs to be accessed to reach the target SNA application. The main drawback to this setup is that the TN3270 Server selection is then static. There is no dynamic criteria for selecting the TN3270 Server, such as the response time. TN3270 Server failures require manual reconfiguration of the TN3270 Clients to point to an alternate active TN3270 Server, since manual configuration usually allows the definition of only a single TN3270 Server and no ability to define a backup TN3270 Server configuration.
Accessing SNA Application from TN3270 Client with Dynamic Configuration
In a TN3270 Client-Server approach, one technique commonly applied is to provide the Intermediate Selection Application via a Web Server implementation. In such a case, the user accesses the Intermediate Selection Application within the Web Server, using his favorite Web Browser running on his user workstation. This approach is described in FIG. 3:
First step 301: The user receives a Selection Screen on the Web Browser from the Intermediate Selection Application in the Web Server. The selection screen may offer three applications: A, B and C. By selecting the desired SNA Application from the Selection Screen (just a click from within the Browser), the workstation obtains the IP addressing/naming information corresponding to the preferred TN3270 Server for the desired target SNA application.
Second step 302: If the user chooses application C from the Selection Screen, the user workstation obtains from the Web Server the address (SS) for the TN3270 Server(s) (providing access to the mainframe housing application C).
Third step 303: Thus, the local TN3270 Client can then be started either manually or automatically to access the preferred Telnet server by using the address provided by the Intermediate Selection Application. The user workstation receives back the address of the Telnet server (Server S which address is SS) and connects to the target application C via the appropriate Server (Telnet Server S). The target application C then presents an Application Welcome Screen to the user (for instance displaying the SNA application name and asking for a user logon and password).
Going through an Intermediate Selection Application shields end-users from changes that inevitably occur, for example, when an SNA application is changed from being run on one server to another server in a different location or when a new SNA application is added. In such cases, only the Selection Screen is modified and changes in target application locations are completely transparent to the users. The workstations"" configurations are not impacted by changes in target application locations.
Problem
The problem is to provide a system and method for automatically configuring the TN3270 Client to use the best TN3270 Server to access the desired SNA Application. Current solutions address the problem of configuring the TN3270 client only partially. TN3270 Clients can be manually configured with the target TN3270 Server. The main drawbacks of this solution are as follows:
(a) There is no dynamic TN3270 Server selection;
(b) When the TN3270 Server is in failure, a manual reconfiguration of the TN3270 Client is required; and
(c) TN3270 Server names or addresses must be known and manually configured by end users for each SNA Application the user wants to access.
(d) Only a xe2x80x9cmanualxe2x80x9d load balancing through the static configuration of the TN3270 Clients is provided.
TN3270 Clients can also be dynamically configured for a target TN3270 Server corresponding to the desired SNA Application using an Intermediate Selection Application running on a dedicated Web Server. The main drawbacks concerning this solution are as follows:
(a) There is no response time consideration in the TN3270 Server selection;
(b) There is no efficient TN3270 Server failure detection (i.e. to access a particular SNA application, the Web Server will always select the same TN3270 Server to the end users, even if that Server has failed);
(c) The connection to the SNA Application is indirect, since the end user has to first manually connect to a Web Server to receive the Selection Screen. This Web Server connection terminates each time the end user wants to access an SNA Application, even if the Intermediate Selection Application is able to determine the best TN3270 Servers and is able to detect TN3270 Server failures.
Current solutions also only partially address the problem of selecting the best TN3270 server. When the TN3270 server is selected according to some response time standards, the response time is usually measured from as to a single system and does not integrate all the network delays between end users and SNA Applications. As a consequence, the measured response time by the single system is not representative of the response time perceived by the entire group of end users. End users are geographically dispersed and a single system cannot take into account the geographical specificities of each end user. For instance measuring the response time of a TN3270 Server located in Paris may not be representative of the response time perceived from Toulouse because the measurement does not integrate the network delay between Toulouse and Paris.
The response time can also be measured from each TN3270 Client, but this solution induces a very heavy load on each user workstation.
When the TN3270 Server is selected according to some anti-failure specifications, failures are usually detected from one system. However, multiple end users are usually accessing the same TN3270 Servers, and those end users are geographically dispersed. A single system will not be able to detect all network failures and cannot take into account the geographical specificities of each end user.
Other solutions provide clustering of TN3270 Servers using an external dispatcher system acting as single logical access point. All TN3270 Clients are manually configured with the address of the external dispatcher system (as the target TN3270 Server). Traffic is then routed to a selected TN3270 Server. An example of such dispatcher is the IBM Interactive network Dispatcher. More information concerning this product can be found in IBM""s publication entitled xe2x80x9cInteractive Network Dispatcher V1.2xe2x80x94User""s Guidexe2x80x9d GC31-8496-01 incorporated herein by reference. Although a dispatcher-oriented solution allows an efficient load balancing in most cases, the main drawbacks are as follows: An additional dedicated system or a specific hardware is required, introducing an additional software layer between end users and SNA Applications (with potential negative effects on performance). Also, the external dispatcher name must be manually configured by end users in their TN3270 Clients.
The present invention optimizes the TN3270 Server selection by using availability and response time criteria. The present invention also optimizes the TN3270 service performance by integrating a response time consideration to the TN3270 Server selection. The present invention insures a better service availability by automatically detecting TN3270 Servers failures. The present invention also integrates the network delay between TN3270 clients and SNA applications when measuring availability and response time of TN3270 servers.
The present invention relates to automatic TN3270 Client configuration and more particularly to a method and system for optimizing the selection of a TN3270 Server according to response time and availability criteria. The method comprises the steps of measuring, using measurement probes from one or a plurality of measurement systems distributed in the IP network, performance and availability of each TN3270 server for accessing one or a plurality of SNA applications; transferring the performance and response time measurements to a single system within the IP network; and selecting within the single system an appropriate TN3270 server for accessing a particular SNA application using the performance and availability measurements.
The present invention also comprises distributed availability and response time probes for retrieving a SNA Application Welcome Screen through each TN3270 Server providing access to the same SNA Application, measuring the associated response time, and detecting TN3270 failures or degradation of response time. The present invention also relates to a Master Probe program for retrieving and aggregating measurement data provided by the distributed availability and response time probes. The present invention uses a CGI (Common Gateway Interface) program for dynamically creating an Autoserver code (in an alternative embodiment, in Javascript language) on an Autoserver URL (Universal Resource Locator) system. The Autoserver code may be used to select the best TN3270 Servers to access the desired SNA Applications according to availability and response time information provided by the Master Probe.
The present invention fixes the drawbacks of the prior solutions by measuring the availability and response time from probes distributed close to end users or groups of end users. Since probes are geographically close to end users, data provided by the probes is representative of the TN3270 service (in terms of availability and response time) observed by the end users. The present invention provides the following advantages:
(a) Early detection of TN3270 Servers failures, providing a high TN3270 service availability;
(b) Integration of a response time factor to the TN3270 Server selection optimizes TN3270 service performances;
(c) TN3270 Servers response time is measured from multiple distributed systems closer to end users;
(d) Because they integrate network delays, these distributed systems provide accurate information concerning the response time perceived by end users;
(e) TN3270 Servers failures are detected from multiple distributed systems closer to end users;
(f) The distributed systems provide an accurate information concerning the failures perceived by the users;
(g) Induced IP and SNA survey traffic is minimized by running the distributed availability and response time probes from a limited number of systems (compared with running the probes from each TN3270 Client system);
(h) Integration of response time degradation in the distributed probes achieves proactive TN3270 Server failure detection;
(i) Periodic updates of xe2x80x9cbestxe2x80x9d or preferred TN3270 Servers can be provided (automatically or on request) to TN3270 Clients.
(j) Useless traffic to failing TN3270 Servers is minimized since failed TN3270 Servers are excluded from the list of available target servers immediately upon proactive detection;
(k) TN3270 Client performances are not degraded because availability and response time data are not processed within the downloaded Autoserver code but rather in the Autoserver URL system;
(l) The TN3270 Client is only connected once (when it is started) to the Autoserver URL system to receive the Autoserver code providing the selection of the best TN3270 Servers;
(m) The TN3270 Client can use a local copy of the Autoserver code if the Autoserver URL system cannot be reached, providing stability; and
(n) The end user need not first connect to an Intermediate Selection Application in order to access a desired SNA Application, since his TN3270 Client is automatically connected to the best TN3270 Server.
Several other advantages will be apparent to one skilled in the art, in light of this disclosure.